Goals. The 5 study goals are: 1) to harness the potential of malpractice insurance programs to operate as a nationwide error reporting system; 2) to identify the most frequent factors contributing to errors found in a focused review of malpractice claims files; 3) to test case-control analysis as a method of quantifying the role of various contributing factors to the occurrence of specific errors; 4) to assess how the patterns of errors and contributing factors detected through claims file analysis compare to those identified in other reporting systems; 5) to use claims data to facilitate design and implementation of a series of targeted patient safety interventions. Methods. Approximately 3,000 claims files from 6 large malpractice insurers will be analyzed. (Together, these insurers cover approximately 35,000 physicians, 60 acute care hospitals, and more than 100 outpatient facilities in 15 states). Using structured review methods, physician reviewers will identify errors, describe their consequences, and judge the contributing role of a wide range of human factors, including environmental conditions (e.g. workload, technology, interruptions), team/group behavior (e.g. inadequate hand-off, communication failures, lack of supervision, failure to follow/break established protocols), and individual factors (e.g. inexperience, technical incompetence). Descriptive analytical techniques will be used to isolate the combinations of factors that are most frequently implicated in specific errors within each of the clinical categories. Two supplementary data sources will support more in-depth analyses: 1) human factors information on 400 "potential claims" reported to risk managers at 5 hospitals; 2) reviews of 720-1280 medical records ("controls"). These data will allow: a) comparison of factors that contributing to errors in potential claims with those detected in actual claims; (b) 3-4. case-control analyses to designed to help target interventions by isolating those factors that are the key causes of specific errors. Interventions. Study findings will guide identification and design of a series of interventions at institutions covered by the participating insurers. Investigators will facilitate institutions' choice, design, and implementation of interventions through: recruitment and orientation of Coordinating Teams; recruitment of Intervention Teams; support of Intervention Teams through a Safety Collaborative, which will include site